Curvilinear duct fabricated with additive manufacturing

ABSTRACT

Curvilinear ducts manufactured by depositing one or more runs of material in a conjoined helix, a conjoined plurality of conjoined planar spirals, and a plurality of conjoined conical spirals.

STATEMENT OF RELATED APPLICATIONS

The following patent applications are incorporated by reference for their description of how to make and use additive manufacturing system 100:

U.S. patent application Ser. No. 15/375,832, filing date Dec. 12, 2016;

U.S. patent application Ser. No. 15/232,767, filing date Aug. 9, 2016;

U.S. patent application Ser. No. 14/574,237, filing date Dec. 17, 2014; and

U.S. patent application Ser. No. 14/623,471, filing date Feb. 16, 2015.

U.S. patent application Ser. No. 15/459,747, filed on Mar. 15, 2017, entitled “Duct Fabricated With Additive Manufacturing” is incorporated by reference for its description of how to manufacture ducts using helices, planar spirals, and conical spirals.

FIELD OF THE INVENTION

The present invention relates to additive manufacturing, which is often colloquially called “3D Printing,” in general, and, more particularly, to manufacturing curvilinear ducts with additive manufacturing.

BACKGROUND

Additive manufacturing is a technique for building a three-dimensional object from a mathematical model of the object. In the additive manufacturing technique called fused-deposition modeling, the object is built by feeding a thermoplastic filament into a heated deposition head. The heated deposition head melts and deposits the molten thermoplastic material as one or more runs of material. Typically, a run of material is shaped like a thread or like the toothpaste that is squeezed from a tube but much smaller. When a run is deposited, it is just slightly above its melting point. After it is deposited, the run quickly solidifies and fuses with the runs that it touches.

Perhaps the greatest advantage of additive manufacturing is that it can build an object of any shape. To accomplish this, however, there are constraints on the sequence in which the runs can be deposited. First, each run must be supported. In other words, a run cannot be deposited on air. Therefore, each run must be deposited on:

-   -   (i) a platform that is not part of the object, or     -   (ii) one or more previously-deposited runs that will be part of         the object, or     -   (iii) a temporary scaffold of support material that is not part         of the object, or     -   (iv) any combination of i, ii, and iii.         Second, when a three-dimensional surface is sealed, it is no         longer possible to deposit a run inside of that surface. This is         analogous to the situation in which once you close a box, you         can't put anything into the box.

There is a general methodology that is used in additive manufacturing that satisfies these constraints and enables the building of an object of any shape. The three-dimensional model of the object is modeled as thousands of thin horizontal layers. Each layer is modeled as thousands of runs and voids. The object is then built, one run at a time, one layer at a time, only in the ±X, ±Y, and +Z directions.

There are, however, costs and disadvantages associated with traditional additive manufacturing.

SUMMARY OF THE INVENTION

Embodiments of the present invention are able to fabricate curvilinear ducts with additive manufacturing without some of the costs and disadvantages for doing so in the prior art. For example, ducts fabricated in accordance with the illustrative embodiments have more advantageous mechanical properties in comparison to ducts fabricated using prior art techniques.

Furthermore, some of the ducts that are manufactured in accordance with the illustrative embodiments comprise a continuous run of material, which enables advantageous mechanical properties in comparison to ducts that are manufactured with a plurality of discontinuous runs of material.

The run of material in some embodiments of the present invention chopped-fiber reinforced thermoplastic. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the run of material is any satisfactory material.

A duct manufactured in accordance with the illustrative embodiment comprises one or more segments, wherein each segment is straight or curved. Furthermore, each segment is manufactured by depositing:

i. one or more conjoined helices, or

ii. one or more stacks of conjoined planar spirals, or

iii. one or more conjoined stacks of conical spirals, or

iv. any combination of i, ii, and iii.

Co-pending U.S. patent application Ser. No. 15/459,747 entitled “Duct Fabricated With Additive Manufacturing” teaches how to make and use straight segments of ducts from helices, stacks of planar spirals, and conical spirals. In order to make curved segments of ducts, however, the dimensions of these structures must be altered.

In particular, the duct axis {right arrow over (d)}(t) is a space curve represented by the vector function: {right arrow over (d)}(t)=<a(t),b(t),c(t)> and the longitudinal axis {right arrow over (r)}(s) of the run of material is a space curve described by the vector function: {right arrow over (r)}(s)=<f(s),g(s),h(s)> The value of the value of the conjoining axis j(t) at {right arrow over (r)}(s) is proportional to the distance between {right arrow over (r)}(s) and the center of curvature {right arrow over (p)}(t): j(t)∝∥{right arrow over (r)}(s)−{right arrow over (p)}(t)∥ This enables the run of material to remain conjoined and form a curved duct.

All dimensions and coordinates in this specification are stated in millimeters in a right-hand Cartesian and/or cylindrical coordinate system. It will be clear to those skilled in the art how to convert from one coordinate system to the other, and both coordinate systems will be used interchangeably. It will, however, be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that use any (small “m”) metric system and any coordinate system.

It will be clear to those skilled in the art, after reading this disclosure, that the geometric descriptions of the illustrative embodiments are ideals and that the imperfection of manufacturing might produce objects with inconsequential differences in dimensions and geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustration of the salient components of additive manufacturing system 100 in accordance with the illustrative embodiment of the present invention.

FIG. 2 depicts an illustration of an orthographic view of duct 151, which is an illustrative embodiment of the present invention.

FIG. 3 depicts an illustration of a cross-sectional view of duct 151.

DETAILED DESCRIPTION

FIG. 1 depicts an illustration of the salient components of additive manufacturing system 100 in accordance with the illustrative embodiment of the present invention. Additive manufacturing system 100 comprises: CAD/CAM system 101, build chamber 102, turn-table 110, deposition platform 111, robotic arm 121 (which itself comprises deposition head 122 and deposition nozzle 123), thermoplastic filament spool 130, and thermoplastic filament 131. The purpose of manufacturing system 100 is to manufacture duct 151.

CAM controller 101 comprises the hardware and software necessary to direct build chamber 102, control robotic arm 121, deposition head 122, deposition nozzle 123, and turntable 110 to manufacture duct 151. It will be clear to those skilled in the art, after reading this disclosure, how to make and use CAM controller 101.

Build chamber 102 is a thermally-insulated, temperature-controlled environment in which duct 151 is manufactured. It will be clear to those skilled in art how to make and use build chamber 102.

Turn-table 110 comprises a stepper motor under the control of CAM controller 101 that is capable of rotating platform 111 (and, consequently duct 151) around the Z-axis. In particular, turn-table 110 is capable of:

-   -   i. rotating platform 111 clockwise around the Z-axis from any         angle to any angle, and     -   ii. rotating platform 111 counter-clockwise around the Z-axis         from any angle to any angle, and     -   iii. rotating platform 111 at any rate, and     -   iv. maintaining (statically) the position of platform 111 at any         angle.         It will be clear to those skilled in the art how to make and use         turn-table 110.

Platform 111 comprises hardware on which duct 151 is manufactured. It will be clear to those skilled in the art how to make and use platform 111.

Robotic arm 121 is a seven-axis arm capable of placing deposition nozzle 123 at any location in the build volume of duct 151 and from any approach angle. Furthermore, robotic arm can move deposition nozzle 123 in:

i. the +X direction,

ii. the −X direction,

iii. the +Y direction,

iv. the −Y direction,

v. the +Z direction,

vi. the −Z direction, and

vii. any combination of i, ii, iii, iv, v, and vi

while rotating the approach angle of deposition nozzle 123 around any point or temporal series of points. It will be clear to those skilled in the art how to make and use robotic arm 121.

Deposition head 122 is hardware that heats and deposits filament 131 (which may partially or wholly contain one or more fiber strands) via deposition nozzle 123.

Thermoplastic filament 131 comprises a continuous tow of carbon fiber that is impregnated with a thermoplastic, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which thermoplastic filament 131 has a different fiber composition as described in U.S. patent application Ser. No. 14/184,010, which is incorporated by reference.

Thermoplastic filament 131 is deposited as a “run of material,” which is not shown in FIG. 1 as distinct from duct 151. The physical and geometric properties of the runs of material are described below and in the accompanying figures.

FIG. 2 depicts an illustration of an orthographic elevation view of duct 151 in accordance with the illustrative embodiment of the present invention.

Duct 151 is a curvilinear duct that is capable of directing the flow of a fluid between opening 231 and 231. The curvature of duct 151 is defined by a three-dimensional space curve called the duct axis {right arrow over (d)}(t).

In order to facilitate an understanding of the present invention, the duct axis {right arrow over (d)}(t) of the illustrative embodiment is confined to a plane. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which duct axis {right arrow over (d)}(t) is not confined to a plane (i.e., duct axis {right arrow over (d)}(t) is a non-linear and a non-planar space curve).

In accordance with the illustrative embodiment, duct axis {right arrow over (d)}(t) is described by a vector function whose general form is: {right arrow over (d)}(t)=<a(t),b(t),c(t)>  (Eq. 1a) where a(t), b(t), and c(t) are functions in a particular coordinate system (e.g., Cartesian, cylindrical, polar, etc.) and t is a real number in the domain t: [t₁, t₂]. It will be clear to those skilled in the art how to describe any space curve, and, therefore, any duct axis as a vector function. Furthermore, it will be clear to those skilled in the art how to represent the space curve of any duct axis using mathematical techniques other than vector functions.

The particular vector function (in Cartesian coordinates) for duct axis {right arrow over (d)}(t) of duct 151 is:

$\begin{matrix} {{a(t)} = {\frac{800}{3}{\cos\left( \frac{\pi\; t}{500} \right)}}} & \left( {{{Eq}.\mspace{14mu} 1}b} \right) \end{matrix}$ b(t)=0  (Eq. 1c) c(t)=s  (Eq. 1d) where t is a real number in the domain t: [0, 1000]. It will be clear to those skilled in the art, after reading this disclosure, how to determine the vector function for any duct axis in any coordinate system.

Duct axis {right arrow over (d)}(t) comprises curves, and the general equation for the curvature κ(t) of duct axis {right arrow over (d)}(t) (expressed independently of any particular coordinate system) is:

$\begin{matrix} {{\kappa(t)} = {\frac{{{d(t)}^{\prime} \times {d(t)}^{''}}}{{{d(t)}^{\prime}}^{3}}.}} & \left( {{{Eq}.\mspace{14mu} 2}a} \right) \end{matrix}$ When the vector function of duct axis {right arrow over (d)}(t) is expressed in Cartesian coordinates, the equation for the curvature κ(t) of is:

$\begin{matrix} {{\kappa(t)} = {\frac{\sqrt{\left( {{c^{''}b^{\prime}} - {c^{\prime}b^{''}}} \right)^{2} + \left( {{a^{''}c^{\prime}} - {a^{\prime}c^{''}}} \right)^{2} + \left( {{b^{''}a^{\prime}} - {a^{''}b^{\prime}}} \right)^{2}}}{\left( {a^{\prime 2} + b^{\prime 2} + c^{\prime 2}} \right)^{2/3}}.}} & \left( {{{Eq}.\mspace{14mu} 2}b} \right) \end{matrix}$ It will be clear to those skilled in the art how to compute the curvature κ(t) of any duct axis for any value of the parameter t.

The radius of curvature δ(t) of duct axis {right arrow over (d)}(t) equals:

$\begin{matrix} {{\delta(t)} = \frac{1}{\kappa(t)}} & \left( {{Eq}.\mspace{14mu} 3} \right) \end{matrix}$ which equals the distance from the duct axis {right arrow over (d)}(t) to the center of curvature {right arrow over (p)}(t), which is a space curve that is described by the vector function: {right arrow over (p)}(t)=<α(t),β(t),γ(t)>  (Eq. 4). where α(t), β(t), and γ(t) are functions in the same coordinate system as that used for describing duct axis {right arrow over (d)}(t). It will be clear to those skilled in the art how to determine the center of curvature {right arrow over (p)}(t) for any duct axis {right arrow over (d)}(t). For example, it is well known to those skilled in the art that the center of curvature {right arrow over (p)}(t) is the point that lies at the radius of curvature δ(t) from duct axis {right arrow over (d)}(t) (i.e., δ(t)=∥{right arrow over (d)}(t)−{right arrow over (p)}(t)∥) in the direction of the unit principal normal vector of duct axis {right arrow over (d)}(t) (into the curve). As space curve {right arrow over (p)}(t) is known as the evolute of {right arrow over (d)}(t). When duct axis {right arrow over (d)}(t) is a planar curve, the evolute of {right arrow over (d)}(t) is also a planar curve. In contrast, when duct axis {right arrow over (d)}(t) is a non-planar space curve, the evolute of {right arrow over (d)}(t) is also a non-planar space curve.

In accordance with the illustrative embodiment, duct 151 comprises a continuous run of material whose longitudinal axis {right arrow over (r)}(s) is a space curve described by the vector function: {right arrow over (r)}(s)=<f(s),g(s),h(s)>  (Eq. 5) where f(s), g(s), and h(s) are functions in the same coordinate system as that used for describing duct axis {right arrow over (d)}(t). It will be clear to those skilled in the art, after reading this disclosure, how to determine the vector function for whose longitudinal axis {right arrow over (r)}(s) for any duct, whether it comprises a helix, one or more planar spirals, or one or more conical spirals.

For curved ducts and the curved portions of curvilinear ducts, the value of the conjoining axis j(t) is a function of t. In particular, the value of the conjoining axis j(t) at {right arrow over (r)}(s) is proportional to the distance between {right arrow over (r)}(s) and the center of curvature {right arrow over (p)}(t): j(t)∝∥{right arrow over (r)}(s)−{right arrow over (p)}(t)∥  (Eq. 6). This enables the run of material to remain conjoined and form a curved duct. In accordance with the illustrative embodiment, the range of j(t) is between 0.1 millimeters and 0.5 millimeters, but it will be clear to those skilled in the art, after reading this disclosure, how to select the values of j(t)—in accordance with Equation 6—for any duct.

The value of the isolating axis i(t) depends on the deposition process and the desired mechanical characteristics of duct 151. For example, the value of the isolating axis i(t) can be a constant: i(t)=I  (Eq. 7a).

Alternatively, the value of the isolating axis i(t) can also vary as a function of the distance from {right arrow over (r)}(s) to the center of curvature {right arrow over (p)}(t): i(t)∝j(t)∝∥{right arrow over (r)}(s)−{right arrow over (p)}(t)∥  (Eq. 7b). In any case, it will be clear to those skilled in the art, after reading this disclosure, how to select the particular values of i(t)—in accordance with equations 7a or 7b—for any duct.

It will be clear to those skilled in the art, after reading this disclosure, how to modify any duct taught in the co-pending patent application entitled “Duct Fabricated With Additive Manufacturing” (U.S. patent application Ser. No. 15/459,747) to have one or more curved segments. For example, any duct can be manufactured by depositing a continuous run of material in the form of a conjoined helix—with any profile including, but not limited to circular and rectangular-with-rounded corners. FIG. 3 depicts a cross-sectional view of duct 151 featuring a rectangular-with-rounded-corners profile. Additionally, any duct can be manufactured by depositing a conjoined stack of conjoined planar spirals—with each planar spiral having any profile including, but not limited to circular and rectangular-with-rounded corners. And still furthermore, any duct can be manufactured by depositing a conjoined stack of conical spirals—with each conical spiral having any profile including, but not limited to circular and rectangular-with-rounded corners.

It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. It is therefore intended that such variations be included within the scope of the following claims and their equivalents. 

What is claimed is:
 1. A duct with a duct axis {right arrow over (d)}(t) described by the vector function: {right arrow over (d)}(t)=<a(t),b(t),c(t)>, the duct comprising: a run of material having a longitudinal axis {right arrow over (r)}(s) described by the vector function: {right arrow over (r)}(s)=<f(s),g(s),h(s)> that forms a helix around the duct axis {right arrow over (d)}(t); wherein the helix is a rectangular-with rounded-corners helix; wherein the duct axis {right arrow over (d)}(t) is characterized by a curvature κ(t) and a center of curvature {right arrow over (p)}(t) described by the vector function: {right arrow over (p)}(t)=<α(t),β(t),γ(t)>; wherein the curvature κ(t)>0; wherein the run of material is characterized by a conjoining axis j(t) at {right arrow over (r)}(s) such that j(t)∝∥{right arrow over (r)}(s)−{right arrow over (p)}(t)∥; and wherein t is a real number in the domain t: [t₁, t₂] and s is a real number in the domain s: [s₁, s₂].
 2. The article of claim 1 wherein the run of material has an isolating axis i(t) at {right arrow over (r)}(s) such that i(t)∝∥{right arrow over (r)}(s)−{right arrow over (p)}(t)∥.
 3. The article of claim 1 wherein the run of material has an isolating axis i(t) at {right arrow over (r)}(s) that is constant.
 4. The article of claim 1 wherein the evolute of {right arrow over (d)}(t) is a non-planar space curve over the interval [t₁, t₂].
 5. The article of claim 1 wherein the run of material is chopped-fiber reinforced thermoplastic.
 6. A duct with a duct axis {right arrow over (d)}(t) described by the vector function: {right arrow over (d)}(t)=<a(t),b(t),c(t)>, the duct comprising: a run of material having a longitudinal axis {right arrow over (r)}(s,k) described by the vector function: {right arrow over (r)}(s,k)=<f(s,k),g(s,k),h(s,k)> that forms a first conical spiral around the duct axis {right arrow over (d)}(t); wherein the duct axis {right arrow over (d)}(t) is characterized by a curvature κ(t) and a center of curvature {right arrow over (p)}(t) described by the vector function: {right arrow over (p)}(t)=<α(t),β(t),γ(t)>; wherein the curvature κ(t)>0; wherein the run of material is characterized by a conjoining axis j(t) at {right arrow over (r)}(s,k) such that j(t)∝∥{right arrow over (r)}(s,k)−{right arrow over (p)}(t)∥; and wherein t is a real number in the domain t: [t₁, t₂], s is a real number in the domain s: [s₁, s₂], and k is an integer.
 7. The article of claim 6 wherein the run of material has an isolating axis i(t) at {right arrow over (r)}(s,k) such that i(t)∝∥{right arrow over (r)}(s,k)−{right arrow over (p)}(t)∥.
 8. The article of claim 6 wherein the run of material has an isolating axis i(t) at {right arrow over (r)}(s,k) that is constant.
 9. The article of claim 6 wherein the evolute of {right arrow over (d)}(t) is a non-planar space curve over the interval [t₁, t₂].
 10. The article of claim 6 further comprising a second conical spiral around the duct axis {right arrow over (d)}(t), wherein the first conical spiral and the second conical spiral are conjoined.
 11. The article of claim 1 wherein the conical spiral is a rectangular-with rounded-corners conical spiral. 